>As a total beginner (learning programming by myself since 2 or 3 years), i am always asking myself, how often "little" things like race conditions break something in production

Rookie mistake (and a shoot-yourself-in-the-foot-at-2-am) mistake coming up:

package main

import ( "fmt" "sync" )

func main() { var wg sync.WaitGroup

for i := 0; i < 10; i++ { wg.Add(1)

		go func() {
			fmt.Printf("i= %d\n", i)
			wg.Done()
		}()
	}
	wg.Wait()

}

https://play.golang.org/p/XDzFq_XK_1

And what about this code:

package main

import "fmt"

func main() {

var intArray []int for i := 0; i < 1000; i++ {

		intArray = append(intArray, i)
		fmt.Printf("i= %d\n", i)
	}

	fmt.Println(intArray)

}

https://play.golang.org/p/UuI4uESZ_f

If you don't care if intArray is in the proper order, you might do something like this:

package main

import ( "fmt" "sync" )

func main() { var wg sync.WaitGroup var intArray []int

for i := 0; i < 1000; i++ { wg.Add(1)

		go func(i int) {
			intArray = append(intArray, i)

			fmt.Printf("i= %d\n", i)
			wg.Done()
		}(i)
	}
	wg.Wait()
	fmt.Println(intArray)

}

What's wrong?

On my multi-core computer (though not on playground), len(intArray) could be as low as 500!

Why?

Because a = append isn't atomic.

Go, which is so pedantic about "stupid" mistakes (including something, changing your mind, and not "unincluding" it), didn't catch this. Not an error and no warning.

But the worst part is that when you loop until 10, it works. You can unit test it, integrate test it, and have it break at any point in time.